Giant outburst from the supergiant fast X-ray transient IGR J17544−2619: accretion from a transient disc?

Romano, P.; Bozzo, E.; Mangano, V.; Esposito, P.; Israel, G. L.; Tiengo, A.; Campana, S.; Ducci, L.; Ferrigno, C.; Kennea, J. A.

doi:10.1051/0004-6361/201525749

Cited by 49 publications

(51 citation statements)

References 35 publications

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“…For this reason we did not consider the case of orbital periods shorter than ∼9 days. We also note that short orbital period systems ( 3−5 days) at X-ray luminosities of 10 36−37 erg s −1 could develop temporary accretion disks Romano et al 2015), whose effect on the accretion process cannot be taken into account in the present version of our computations. We plan to include all these complications in future improved versions of the simulations presented here.…”

Section: Discussionmentioning

confidence: 95%

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

Bozzo

Oskinova

Feldmeier

et al. 2016

A&A

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The accretion of the stellar wind material by a compact object represents the main mechanism powering the X-ray emission in classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. In this work we present the first attempt to simulate the accretion process of a fast and dense massive star wind onto a neutron star, taking into account the effects of the centrifugal and magnetic inhibition of accretion ("gating") due to the spin and magnetic field of the compact object. We made use of a radiative hydrodynamical code to model the nonstationary radiatively driven wind of an O-B supergiant star and then place a neutron star characterized by a fixed magnetic field and spin period at a certain distance from the massive companion. Our calculations follow, as a function of time (on a total timescale of several hours), the transitions of the system through all different accretion regimes that are triggered by the intrinsic variations in the density and velocity of the nonstationary wind. The X-ray luminosity released by the system is computed at each time step by taking into account the relevant physical processes occurring in the different accretion regimes. Synthetic lightcurves are derived and qualitatively compared with those observed from classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. Although a number of simplifications are assumed in these calculations, we show that taking into account the effects of the centrifugal and magnetic inhibition of accretion significantly reduces the average X-ray luminosity expected for any neutron star wind-fed binary. The present model calculations suggest that long spin periods and stronger magnetic fields are favored in order to reproduce the peculiar behavior of supergiant fast X-ray transients in the X-ray domain.

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Section: Discussionmentioning

confidence: 95%

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

Bozzo

Oskinova

Feldmeier

et al. 2016

A&A

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“…In the case of IGR J17544-2619, the presence of such structures was first suggested by Romano et al (2015) based on the peak luminosity achieved during an outburst on 2014 October 10 that was too high to be produced within a wind-fed system. No direct evidence of disks in SFXTs has been reported so far.…”

Section: Discussionmentioning

confidence: 99%

Multi-wavelength observations of IGR J17544-2619 from quiescence to outburst

Bozzo

Bhalerao

Pradhan

et al. 2016

A&A

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In this paper we report on a long multi-wavelength observational campaign of the supergiant fast X-ray transient prototype IGR J17544-2619. A 150 ks-long observation was carried out simultaneously with XMM-Newton and NuSTAR, catching the source in an initial faint X-ray state and then undergoing a bright X-ray outburst lasting approximately 7 ks. We studied the spectral variability during outburst and quiescence by using a thermal and bulk Comptonization model that is typically adopted to describe the X-ray spectral energy distribution of young pulsars in high mass X-ray binaries. Although the statistics of the collected X-ray data were relatively high, we could neither confirm the presence of a cyclotron line in the broad-band spectrum of the source (0.5-40 keV), nor detect any of the previously reported tentative detections of the source spin period. The monitoring carried out with Swift /XRT during the same orbit of the system observed by XMM-Newton and NuSTAR revealed that the source remained in a low emission state for most of the time, in agreement with the known property of all supergiant fast X-ray transients being significantly sub-luminous compared to other supergiant X-ray binaries. Optical and infrared observations were carried out for a total of a few thousand seconds during the quiescence state of the source detected by XMM-Newton and NuSTAR. The measured optical and infrared magnitudes were slightly lower than previous values reported in the literature, but compatible with the known micro-variability of supergiant stars. UV observations obtained with the UVOT telescope on-board Swift did not reveal significant changes in the magnitude of the source in this energy domain compared to previously reported values.

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“…2007). Extremely large sporadic outbursts indicate that this system can also be affected by short periods of disk accretion, especially when soft X-ray luminosity (proportional to Ṁ ) increases significantly Romano et al 2015). This type of variability of 4U1700-37 is the main focus of the present investigation.…”

Section: Rxtementioning

confidence: 90%

X-Ray Spectra of the High-Mass X-Ray Binary 4u 1700-37 Using Bepposax, Suzaku, and Rxte Observations

Seifina

Titarchuk

Shaposhnikov

2016

ApJ

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We present an X-ray spectral analysis of the high-mass binary 4U1700-37 during its hard-soft state evolution. We use BeppoSAX, Suzaku, and Rossi X-ray Timing Explorer observations for this investigation. We argue that the X-ray broadband spectra during all of the spectral states can be adequately reproduced by a model consisting of a low-temperature blackbody component, two Comptonized components which are both due to the presence of a Compton cloud (CC) that up-scatters seed photons of T s1 1.4 keV and T s2 <1 keV, and an iron-line component. Using this model, we find that the photon power-law index is almost constant, Γ 1 ∼2 for all spectral states. However, Γ 2 shows behavior that is dependent on the spectral state. Namely, Γ 2 is quasi-constant at the level of Γ 2 ∼2 while the CC plasma temperature kT e 2 ( ) is less than 40 keV; on the other hand, Γ 2 is in the range of 1.3<Γ 2 <2 when kT e 2 ( ) is greater than 40 keV. We explain this quasi-stability of Γ during most of the hard-soft transitions of 4U1700-37 in the framework of a model in which the resulting spectrum is described by two Comptonized components. We find that these Comptonized spectral components of the high-mass X-ray binaries 4U1700-37 are similar to those previously found in neutron star (NS) sources. This index dependence versus both the mass accretion rate and kT e revealed in 4U1700-37 is universal observational evidence for the presence of an NS in 4U 1700-37.

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Giant outburst from the supergiant fast X-ray transient IGR J17544−2619: accretion from a transient disc?

Cited by 49 publications

References 35 publications

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

Clumpy wind accretion in supergiant neutron star high mass X-ray binaries

Multi-wavelength observations of IGR J17544-2619 from quiescence to outburst

X-Ray Spectra of the High-Mass X-Ray Binary 4u 1700-37 Using Bepposax, Suzaku, and Rxte Observations

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